1. Field of the Invention
The invention relates to a method for manufacturing parts for rotary machines, especially turbine wheel disks, having a hub bore, as well as turbine wheel disks manufactured by the method, wherein the hub region or the entire part is cooled with a coolant fluid, preferably water, in order to product internal compressive strains in the hub region after the initial treatment, for instance at temperatures of approximately 600.degree. C. In particular, the invention relates to the manufacture of turbine wheel disks for low-pressure rotors, which have bores for receiving twist-prevention bolts.
Internal compressive strains in the vicinity of the surface of hub bores are known to lessen the danger of stress corrosion. Areas threatened by stress corrosion include those surrounding of twist-prevention bores in turbine rotors.
2. Description of the Related Art
It is known from the prior art to subject metal parts of rotary machines having a hub bore to an initial treatment at temperatures of approximately 600.degree. C., for example. In combination with this treatment, it is also known to cool down the hub region of such a part with a cooling fluid, preferably water, faster than the remaining region of the part. The hub region that is chilled first is subjected to severe pressure during the cooling of the remaining part, resulting in internal compressive strains. However, with the usual geometries of rotating parts, especially turbine wheel disks, an internal compressive strain profile arises during this treatment which, as will be described in further detail below with reference to the drawing, exhibits the most severe internal compressive strains in the center of the hub bore, while the least internal compressive strains arise in the axially outer regions of the hub bore. Such a profile is not necessarily optimal in terms of the strains that occur subsequently, because the twist-prevention bores, for example, are disposed in the outer regions. No provisions for changing the profile of tangential internal compressive strains have been known heretofore.